The United States and Europe back the U.N.-mandated Mali operation as a counterstrike against the threat of radical Islamist jihadists using the West African state’s inhospitable Sahara desert as a launching pad for international attacks.

In an overnight assault on Gao backed by French warplanes and helicopters, French special forces seized the town’s airport and a key bridge over the River Niger, killing an estimated dozen Islamist fighters without suffering any losses or injuries, the French army said.

“The Malian army and the French control Gao today,” Malian army spokesman Lieutenant Diaran Kone told Reuters.

The speed of the French action in a two-week-old campaign suggested French and Malian government troops intended to drive aggressively into the north of Mali in the next few days against other Islamist rebel strongholds, such as Timbuktu and Kidal.

There have been 30 French airstrikes on militant targets around Gao and Timbuktu in the past 36 hours.

News that the French and Malian troops were at Gao, the largest northern town held by the Islamists, came as African states struggled to deploy their intervention force in Mali, known as AFISMA, under a U.N. mandate.

Regional army chiefs said on Saturday that a total of 7,700 African soldiers would be dispatched, up from 5,700.

Liberia, Guinea-Bissau, Burundi, Guinea and Uganda are due to join the mission but it was not clear if progress had been made at meetings in Abidjan or Addis Ababa to overcome gaps in transport, equipment and financing.

French army spokesman Colonel Thierry Burkhard said French forces had come under fire from rebel fighters inside Gao, but that both the bridge and airport runway were undamaged.

In Paris, the French defence ministry said Malian and French troop reinforcements were brought in and that soldiers from Chad and Niger, who have experience in desert warfare, were also flown in.

These Malian and regional troops would have the task of securing Gao and its surrounding area, the ministry said.

To the west, French forces recaptured Lere, on the road to Timbuktu, and were advancing, a Malian military source said, asking not be named.

For two weeks, French jets and helicopter gunships have been harrying the retreating Islamists, attacking their vehicles, command posts and weapons depots. The French action had stymied a sudden Islamist offensive launched in early January that had threatened Bamako, Mali’s capital in the south of the country.

Reacting to the French-led offensive, one of the leaders of the alliance of Islamist groups occupying Mali’s north promised resistance to what he called the “new Crusader aggression,” in comments published by al Jazeera’s Arabic website.

Yahya Abu Al-Hamman, leader in the Sahel of Al Qaeda’s North African wing AQIM, which along with Malian militant group Ansar Dine and AQIM splinter MUJWA occupies Mali’s north, said a “Jihadist Islamist emirate” would be created in the territory.

Washington and European governments, while providing airlift and intelligence support to the antimilitant offensive in Mali, are not planning to send in any combat troops.